Characteristic polynomial help

  • Thread starter roryhand
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  • #1
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y^(7)-y^(6)-2y^(4)+2y^(3)+dy-y=0

Note: There is exactly one real zero of the characteristic polynomial and it
has multiplicity 3 (it is a positive integer!). The other zeros are complex
and they have multiplicity 2.

Sadly I missed this lecture day, and am unsure of where to start. Any diffeq demi-gods out there?
 

Answers and Replies

  • #2
Pyrrhus
Homework Helper
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For an equation of order n, if a root (say r1) has a multiplicity s (s =< n), where x is the independent variable

[tex] e^{r_{1}x}, xe^{r_{1}x}, x^{2} e^{r_{1}x}, ..., x^{s-1} e^{r_{1}x} [/tex]

For complex roots, let's say [itex] a+bi [/itex] is repeated s times, then the complex conjugate [itex] a-bi [/itex] is also repeated s times, therefore the solutions for real valued functions, where x is the independent variable:

[tex] e^{ax} \cos{bx}, e^{ax} \sin{bx}, xe^{ax} \cos{bx}, xe^{ax} \sin{bx},..., x^{s-1} e^{ax} \cos{bx}, x^{s-1} e^{ax} \sin{bx} [/tex]
 

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